The group of Senators, led by Ed Markey of Massachusetts, sent a list of questions about privacy practices to major mobile carriers Verizon, AT&T, T-Mobile and Sprint, and internet service providers Charter and CenturyLink.

The questions focus primarily on the company’s policies regarding the use of sensitive user information for the purposes of advertising.

Many of the queries posed by the Senators revolve around some of the requirements that would have been imposed on the ISPs had the Broadband Consumer Privacy Rules, passed by the Federal Communications Commission in October 2016 under President Barack Obama.

The list of 16 questions, which closes with a request for ISPs to disclose any changes they have made to their privacy policies since the repeal of the Broadband Consumer Privacy Rules, was signed by Senators Al Franken of Minnesota, Richard Blumenthal of Connecticut, Elizabeth Warren of Massachusetts, Bernie Sanders and Patrick Leahy of Vermont, Ron Wyden of Oregon and Chris Van Hollen Maryland.